The present invention relates to a method of processing a specimen, such as semiconductor substrates and liquid crystal substrates. More specifically, the present invention relates to a method of processing a semiconductor device which includes an in-situ measuring feature that involves the measurement of particles suspended in a processing chamber (vacuum processing chamber) used for forming and processing (e.g., etching) a thin film.
Processes using plasma are widely used in semiconductor production and liquid crystal display apparatus substrate production, e.g., in etching apparatuses. FIG. 28 shows an example of a plasma processing apparatus in the form of a parallel electrodes type plasma etching apparatus. As shown, this type of apparatus uses a high-frequency signal from a signal generator 83 to modulate the output potential from a power amp 84. This high-frequency potential is split up into two components using a distributor 85 and the components are applied to an upper electrode 81 and a lower electrode 82, respectively, which are disposed in parallel to each other in a processing chamber. Discharge between the two electrodes 81, 82 generates a plasma 71 from an etching gas. Etching is performed on the semiconductor wafer, e.g., a semiconductor substrate (wafer) W. The high-frequency signal can be, for example, a signal with a frequency of approximately 400 kHz.
In this plasma etching apparatus, it is known that the etching reaction product from the plasma operation is also deposited on the wall surface of the plasma processing chamber or the electrodes. As time goes by, the product peels off and forms suspended fine particles. As soon as the etching operation is completed and the plasma discharge stops, these suspended fine particles drop onto the wafer and adhere thereto as contaminants, which reduces the circuit properties and causes visual pattern defects. Ultimately, these adhered contaminants reduce the yield late in a semiconductor apparatus fabrication line and reduce the reliability of the elements.
Many types of apparatus for inspecting wafers for contaminants that have adhered to the surface of the wafer have been proposed and implemented, but these types of apparatuses sample a wafer for inspection from a large number of wafers treated by a plasma processing apparatus. By the time the presence of a contaminant on the sample wafer is recognized, the processing of the other wafers in the lot has already begun. This leads to clusters of defects and a reduced yield. Also, evaluations performed after processing cannot determine the distribution or changes over time of contaminants inside the processing chamber.
Thus, there is a need in the field of semiconductor fabrication, liquid crystal fabrication, and related technology for performing in-situ real-time monitoring of the contamination status in processing chambers.
The sizes of fine particles suspended in the processing chamber range from submicrons to several hundred microns. In the semiconductor field, where the integration scale is growing to include 256 Mbit DRAMs (Dynamic Random Access Memory) and 1 Gbit DRAMs, the minimum circuit pattern width is decreasing to 0.25-0.18 microns. Thus, there is a need to detect contaminants having sizes down to the order of submicrons.
Conventional technologies for monitoring fine particles suspended in processing chambers (vacuum processing chambers), such as plasma processing chambers, are described in Japanese laid-open patent publication number 57-118630 (background technology 1), Japanese laid-open patent publication number 3-25355 (background technology 2), Japanese laid-open patent publication number 3-147317 (background technology 3), Japanese laid-open patent publication number 6-82358 (background technology 4), Japanese laid-open patent publication number 6-124902 (background technology 5), and Japanese laid-open patent publication number Hei 10-213539 (background technology 6).
The background technology 1 concerns a vaporization apparatus equipped with means for illuminating a reaction space with parallel light rays having a spectrum different from the spectrum of the self-emitted light of the reaction space; and means for receiving parallel light illumination and detecting light scattered by fine particles generated in the reaction space.
The background technology 2 concerns an apparatus for measuring fine particles that uses scattering of laser light to measure fine particles that have adhered to a semiconductor device substrate surface and suspended fine particles. The apparatus for measuring fine particles is equipped with a laser beam phase modulator generating two laser beams modulated at predetermined frequencies having identical wavelengths and mutual phase differences; an optical system which causes the two laser beams to intersect in a space containing the fine particles to be measured; an optical detection system receiving light scattered by the fine particles to be measured in the region where the two laser beams intersect and converting the light into an electrical signal; and a signal processor extracting a signal component from the electrical signal generated by the scattered light where the frequency is identical or twice the frequency of a phase modulation signal from the laser light phase modulator and the phase difference with the phase modulation signal is constant in time.
The background technology 3 concerns a method of measuring the contamination status in a reaction container that includes a step of performing scanning illumination with coherent light and generating scattered light in the reaction container and a step of detecting the scattered light in the reaction container. The scattered light is analyzed to measure the contamination status.
The background technology 4 concerns a particle detector equipped with laser means generating a laser beam; scanner means using the laser light to scan a region in a reaction chamber of a plasma processing apparatus containing particles to be measured; a video camera generating a video signal of laser light scattered by particles in the region) and means for processing and displaying an image from the video signal.
The background technology 5 concerns a plasma processing apparatus equipped with a camera device for observing a plasma generating region in a plasma processing chamber; a data processing module for processing an image obtained from the camera device to obtain desired information; and a control module for controlling at least one of the following elements to reduce particles based on information obtained by the data processing module: evacuating means; process gas introducing means; high-frequency potential applying means; and purge gas introducing means.
The background technology 6 concerns a fine particle sensor including a light emitter for sending out a light beam illuminating a space to be measured; a detector containing an optical detector and an optical system focusing the scattered light from the space to be measured and directing it to the optical detector, the arrangement being set up so that the optical detector generates a signal representing the intensity of the light directed toward the optical detector; a pulse detector connected to the optical detector to analyze the signal from the optical detector, and detecting pulses in the signal from the optical detector; and signal processing means containing an event detector detecting a series of pulses resulting from scattered light generated by fine particles accompanying multiple illuminations by the beam while it moves in the measurement space.
In the conventional technologies described above, a laser beam is sent in through an observation window disposed on a side surface of a processing apparatus. A different observation window from the laser entry observation window is disposed on the facing surface or another side surface to allow detection of front-scattering or side-scattering of the laser light. Thus, in these systems for detecting front-scattered light and side-scattered light, the illumination optical system and the detection optical system are formed as different units and two observation windows are needed to accommodate these systems. Also, optical axis adjustments and the like need to be performed for both the illumination and detection optical systems, making operation difficult.
Also, an observation window is almost always disposed on the side surface of a plasma processing chamber to allow monitoring of plasma emission and the like, but in many cases only one observation window is provided. Thus, the conventional methods that require two observation window cannot be implemented for fabrication devices with a processing chamber that only has one observation window.
Furthermore, in conventional systems that detect front-scattered light and side-scattered light, the illumination beam sent into the processing chamber is rotationally scanned. Observation of fine particle generation over the entire surface of the semiconductor wafer requires multiple observation windows and detection optical systems, leading to significant cost increases. Also, providing multiple observation windows and detection optical systems is extremely difficult in practice due to space factor restrictions.
In semiconductor fields where integration is proceeding to the levels of 256 Mbit DRAMs and 1 Gbit DRAMs, the minimum circuit pattern width is being reduced down to 0.25-0.18 microns, creating the need to detect contaminants with sizes on the order of submicrons. However, with the conventional technologies, separating light scattered by fine particles from plasma emission is difficult, so that these technologies have been restricted to use in measuring relatively large fine particles, while detection of very fine particles with sizes on the order of submicrons is difficult.
The present invention solves the problems which are described above.
According to feature of the embodiments of the present invention, a method of processing a semiconductor device comprises the steps of generating plasma in a processing chamber to form a thin film on a semiconductor device or to process a thin film formed on a semiconductor device, scanning a laser beam which is intensity modulated at a desired frequency inside the processing chamber where the semiconductor device is being processed by the plasma through a window, receiving by a sensor through the window a back scattered light being scattered from fine particles suspended in said processing chamber by scanning the laser, detecting said desired frequency component from a signal outputted from the sensor, obtaining information from the detected desired frequency component relating to quantity, size and distribution of fine particles illuminated by said laser beam inside the processing chamber, and outputting said obtained information relating to quantity, size and distribution of the fine particles.
According to another feature of the embodiments of the present invention, a method of processing a semiconductor device comprises the steps of coating resist on a surface of a substrate, exposing said resist coated on said substrate with a desired light pattern, developing said exposed resist, processing said substrate with plasma and the surface of the substrate which is partially covered with the developed resist, and removing said resist coated on the substrate on which said patterns are formed, wherein, in the processing step, the substrate is processed in a processing apparatus and a laser beam is scanned inside the processing apparatus through a window of the processing apparatus and a back scattered light from fine particles by the scanned laser beam is detected through the window.
According to another feature of the embodiments of the present invention, a method of processing a semiconductor device comprises the steps of forming a thin film on a substrate, coating a resist on said substrate on which said thin film is formed, exposing said resist with a light pattern by using an exposing apparatus, developing said exposed resist by using a developing apparatus, etching said thin film on which said resist is developed and forming hole patterns by using a plasma etching apparatus, and removing said resist coated and developed on said substrate on which said hole patterns are formed in said thin film, wherein, in said etching step, a laser beam is scanned inside said plasma etching apparatus where a plasma is generated and back-scattered light from fine particles suspended inside said plasma etching apparatus is detected by a sensor shielded from light reflected from a wall of said plasma etching apparatus.
Furthermore, according to another feature of the embodiments of the present invention, a method of processing a semiconductor device comprises the steps of loading a substrate into a chamber of a plasma etching apparatus, on a surface of the substrate, a resist pattern is formed, evacuating the inside of said chamber in which said substrate is loaded and supplying a process gas inside said chamber, applying high frequency power to an electrode of said plasma etching apparatus and generating plasma inside said chamber, processing said substrate with said plasma, illuminating a laser beam inside said chamber through a window of said plasma etching apparatus and detecting through said window a back-scattered light generated by fine particles suspended inside said chamber, and unloading said substrate from said plasma etching apparatus after stopping said supply of said process gas and evacuating said process gas from inside said chamber.
These and other objects, features and advantages of the invention will be apparent from the following more particular description of preferred embodiments of the invention, as illustrated in the accompanying drawings.